1,721,138 research outputs found
A simple method for the production of large volume 3D macroporous hydrogels for advanced biotechnological, medical and environmental applications
Full text linkThe development of bulk, three-dimensional (3D), macroporous polymers with high permeability, large surface area and large volume is highly desirable for a range of applications in the biomedical, biotechnological and environmental areas. The experimental techniques currently used are limited to the production of small size and volume cryogel material. In this work we propose a novel, versatile, simple and reproducible method for the synthesis of large volume porous polymer hydrogels by cryogelation. By controlling the freezing process of the reagent/polymer solution, large-scale 3D macroporous gels with wide interconnected pores (up to 200??m in diameter) and large accessible surface area have been synthesized. For the first time, macroporous gels (of up to 400?ml bulk volume) with controlled porous structure were manufactured, with potential for scale up to much larger gel dimensions. This method can be used for production of novel 3D multi-component macroporous composite materials with a uniform distribution of embedded particles. The proposed method provides better control of freezing conditions and thus overcomes existing drawbacks limiting production of large gel-based devices and matrices. The proposed method could serve as a new design concept for functional 3D macroporous gels and composites preparation for biomedical, biotechnological and environmental applications
Real-time imaging of complex nanoscale mechanical responses of carbon nanotubes in highly compressible porous monoliths
No full textA facile and rapid assembly of powdered carbon nanotubes (CNTs) into compressible, porous, macroscale monoliths is reported. Despite a Poisson’s ratio just above zero, we found that the sample under compression inside a scanning electron microscope (SEM) revealed CNT regions behaving in auxetic and vortex-like rotational modes as well as standard collapse responses. This method is crucial in understanding the macroscale behaviour based on the accumulation of nanoscale responses to an applied force
Synthesis and application of hydride silica composites for rapid and facile removal of aqueous mercury
No full textThe adsorption of ionic mercury(II) from aqueous solution on functionalized hydride silicon materials was investigated. The adsorbents were prepared by modification of mesoporous silica C-120 with triethoxysilane or by converting alkoxysilane into siloxanes by reaction with acetic acid. Mercury adsorption isotherms at 20?°C are reported, and maximum mercury loadings were determined by Langmuir fitting. Adsorbents exhibited efficient and rapid removal of ionic mercury from aqueous solution, with a maximum mercury loading of approximately 0.22 and 0.43 mmol of Hg g?1 of silica C-120 and polyhedral oligomeric silsesquioxane (POSS) xerogel, respectively. Adsorption efficiency remained almost constant from pH 2.7 to 7. These inexpensive adsorbents exhibiting rapid assembly, low pH sensitivity, and high reactivity and capacity, are potential candidates as effective materials for mercury decontamination in natural waters and industrial effluents
A new coupled non-thermal plasma and sorption method for treatment of liquid radioactive wastes: design and on-site application to Chornobyl NPP-derived wastes
No full textHigher activity liquid wastes pose a significant management challenge at nuclear sites, and there is a strong drive to develop cost-effective (and more sustainable) waste treatment solutions that can remove radioactive and other contaminants from these liquid radioactive wastes (LRW) prior to their discharge or final storage/disposal. Here, results are presented from an on-site trial of a coupled non-thermal plasma / sorption-based LRW treatment system at the “Dibrova” Object in the Chornobyl Exclusion Zone. Over 2m3 of Cs-137 and Sr-90 contaminated LRW from settling tanks used for the holding of tailings and drain water from Chornobyl Building № 5 and deactivation solutions (used in the liquidation efforts following the 1986 Chornobyl disaster) were treated. The coupled treatment process removed greater than 90 % of Cs-137 and Sr-90 from the most contaminated liquids (containing 75 Bq/kg (Cs-137) and 195 Bq/kg (Sr-90)), generating a low mass (<100g ) iron-rich solid residue suitable for onward storage/disposal. Treatment efficiencies for other waste components (e.g. nitrites, phosphates and COD) were equivalent to or exceeded those previously reported for treatment of environmental liquid wastes by similar Advanced Oxidation Processes. The power requirements of the system (due to the pulsed nature of the plasma generated) were relatively low, at 10 kWh, for a LRW treatment rate of 15 - 20 L/h. The system can be operated remotely in autonomous mode, and its modular, easily transportable nature means that the process can be readily adapted for various on-site treatment scenarios.</p
The use of composite ferrocyanide materials for treatment of high salinity liquid radioactive wastes rich in cesium isotopes
Full text linkThe use of composite materials based on metal ferrocyanides combined with natural mineral sorbents for treatment of high salinity Cs-containing liquid radioactive waste (LRW) was investigated. The study indicated that among the investigated composites, the best sorption characteristics for Cs were shown by materials based on copper ferrocyanide. Several factors affecting the removal of cesium from LRW, namely total salt content, pH and organic matter content, were also investigated. High concentrations of complexing organic matter significantly reduced the sorption capacity of ferrocyanide sorbents
Creation of 3-dimensional carbon nanostructures from UV irradiation of carbon dioxide at room temperature
No full textA method is presented for the production of carbon nanomaterials from carbon dioxide in a low temperature process. In this method, carbon dioxide is irradiated with an ultraviolet laser at the conditions of critical opalescence where light is scattered and absorbed. Spherical carbon nanoparticles are obtained under these conditions on metal substrates without any additional catalyst near room temperature. The particles are of approximately uniform shape and size of around 100 nm. Some of the particles form clusters. The method is reproducible on different substrates. Quantum chemical calculations have been employed in order to elucidate the role of critical opalescence and of the substrate. The calculations show that the presence of molecular clusters at the critical point is essential in decreasing the excitation energy. The dissociation reaction most likely occurs on the surface of the substrate, where the excitation energy is decreased even further
Novel nanostructured iron oxide cryogels for arsenic (As(III)) removal
Full text linkNovel macroporous iron oxide nanocomposite cryogels were synthesized and assessed as arsenite (As(III)) adsorbents. The two-step synthesis method, by which a porous nanonetwork of iron oxide is firstly formed, allowed a homogeneous dispersion of the iron oxide in the cryogel reaction mixture, regardless of the nature of the co-polymer forming the cryogel structure. The cryogels showed excellent mechanical properties, especially the acrylamide-based cryogel. This gel showed the highest As(III) adsorption capacity, with the maximum value estimated at 118 mg/g using the Langmuir model. The immobilization of the nanostructured iron oxide gel into the cryogel matrix resulted in slower adsorption kinetics, however the cryogels offer the advantage of a stable three-dimensional structure that impedes the release of the iron oxide nanoparticles into the treated effluent. A preliminary toxicity evaluation of the cryogels did not indicate any apparent inhibition of human hepatic cells activity, which together with their mechanical stability and high adsorption capacity for As(III) make them excellent materials for the development of nanoparticle based adsorption devices for drinking water treatment.</p
High efficiency removal of dissolved As(III) using iron nanoparticle-embedded macroporous polymer composites
No full textNovel nanocomposite materials where iron nanoparticles are embedded into the walls of a macroporous polymer were produced and their efficiency for the removal of As(III) from aqueous media was studied. Nanocomposite gels containing ?-Fe2O3 and Fe3O4 nanoparticles were prepared by cryopolymerisation resulting in a monolithic structure with large interconnected pores up to 100 ?m in diameter and possessing a high permeability (ca. 3 × 10?3 m s?1). The nanocomposite devices showed excellent capability for the removal of trace concentrations of As(III) from solution, with a total capacity of up to 3 mg As/g of nanoparticles. The leaching of iron was minimal and the device could operate in a pH range 3–9 without diminishing removal efficiency. The effect of competing ions such as SO42? and PO43? was negligible. The macroporous composites can be easily configured into a variety of shapes and structures and the polymer matrix can be selected from a variety of monomers, offering high potential as flexible metal cation remediation devices
In Vivo Scaffold Fabrication
No full textTwo-photon-polymerisation is a rapidly developing technique for the micro- and nanofabrication of three dimensional structures. Its high resolution and the full accessibility of the 3rd order of dimension render it the ideal technique for applications in nanophotonics and biomedicine. Its wide selection of applicable materials makes it especially promising in the field of biomedicine. The 2PP technique permits the reproduction of complex anatomic structures specifically favouring the fabrication of custom made polymeric scaffolds. 2PP structuring does not harm biological tissue since there is a window of transparency for biological material within the used wavelengths. The challenge is to fabricate scaffolds directly in vivo.
This poster reports the fabrication of scaffolds using (meth)acrylate-based photopolymers with embedded living organisms (Caenorhabditis elegans). The structuring was performed with a pulsed laser with a wavelength of 810nm and adjustable power up to 160mW. Using a 20x magnification microscope objective with a numerical aperture of 0.4, a high resolution scaffold with a base area of 300x300µm and a height of 80µm could be fabricated. Taking advantage of high laser intensities (writing speed: 300µm/s) the structuring process took only 12 minutes.
As the stress response of biological material to NIR light is negligible, one can consider environmental stress of chemical origin only. To optimize the conditions we tested the toxicity and reactivity of different resins with a focus on water-based, biocompatible and biodegradable hydrogels together with water soluble, near-infrared initiators suitable for 2PP
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